cmd/geth: add --config file flag (#13875)

* p2p/discover, p2p/discv5: add marshaling methods to Node

* p2p/netutil: make Netlist decodable from TOML

* common/math: encode nil HexOrDecimal256 as 0x0

* cmd/geth: add --config file flag

* cmd/geth: add missing license header

* eth: prettify Config again, fix tests

* eth: use gasprice.Config instead of duplicating its fields

* eth/gasprice: hide nil default from dumpconfig output

* cmd/geth: hide genesis block in dumpconfig output

* node: make tests compile

* console: fix tests

* cmd/geth: make TOML keys look exactly like Go struct fields

* p2p: use discovery by default

This makes the zero Config slightly more useful. It also fixes package
node tests because Node detects reuse of the datadir through the
NodeDatabase.

* cmd/geth: make ethstats URL settable through config file

* cmd/faucet: fix configuration

* cmd/geth: dedup attach tests

* eth: add comment for DefaultConfig

* eth: pass downloader.SyncMode in Config

This removes the FastSync, LightSync flags in favour of a more
general SyncMode flag.

* cmd/utils: remove jitvm flags

* cmd/utils: make mutually exclusive flag error prettier

It now reads:

   Fatal: flags --dev, --testnet can't be used at the same time

* p2p: fix typo

* node: add DefaultConfig, use it for geth

* mobile: add missing NoDiscovery option

* cmd/utils: drop MakeNode

This exposed a couple of places that needed to be updated to use
node.DefaultConfig.

* node: fix typo

* eth: make fast sync the default mode

* cmd/utils: remove IPCApiFlag (unused)

* node: remove default IPC path

Set it in the frontends instead.

* cmd/geth: add --syncmode

* cmd/utils: make --ipcdisable and --ipcpath mutually exclusive

* cmd/utils: don't enable WS, HTTP when setting addr

* cmd/utils: fix --identity

1 files changed, 25 insertions, 0 deletions

diff --git a/p2p/netutil/net.go b/p2p/netutil/net.go
index 3c3715788..f6005afd2 100644
--- a/p2p/netutil/net.go
+++ b/p2p/netutil/net.go
@@ -84,6 +84,31 @@ func ParseNetlist(s string) (*Netlist, error) {
 	return &l, nil
 }
 
+// MarshalTOML implements toml.MarshalerRec.
+func (l Netlist) MarshalTOML() interface{} {
+	list := make([]string, 0, len(l))
+	for _, net := range l {
+		list = append(list, net.String())
+	}
+	return list
+}
+
+// UnmarshalTOML implements toml.UnmarshalerRec.
+func (l *Netlist) UnmarshalTOML(fn func(interface{}) error) error {
+	var masks []string
+	if err := fn(&masks); err != nil {
+		return err
+	}
+	for _, mask := range masks {
+		_, n, err := net.ParseCIDR(mask)
+		if err != nil {
+			return err
+		}
+		*l = append(*l, *n)
+	}
+	return nil
+}
+
 // Add parses a CIDR mask and appends it to the list. It panics for invalid masks and is
 // intended to be used for setting up static lists.
 func (l *Netlist) Add(cidr string) {